In order to determine the relationship between leaf area and girth of P. deltoids trees grown in Charsadda district of NWFP area, simple, multiple and double log regression analysis was carried out. Girth of the tree was used as dependent variable and leaf area, age and space were used as independent variables. In this regard, data were collected from 2 and 7 years old compact plantations, 3 years intercropping plantation and 8 years linear plantations It was found that simple regression equations showed better predictability in terms of F-value and R-square estimates. The highest correlation between girth and leaf area was estimated at the age of two years because of higher photosynthetic activity due to large leaf surface area, while the lowest relationship between girth and leaf area was found at the age of 8 years because of maturity of the tree crops. Leaf area/girth ratio decreased from 2 years to 8 years. Leaf area, age and spacing explained about 84.5 percent of total variation in the girth of the trees.